Temptation - Or - Ie Sucks

Sooo, I was looking at the source code for Yelp, thinking that it's interesting that they use the semantical niceness of a definition list for the hours and whatnot on listings, and I notice that this is how the content area container begins:

First time I've seen something like that on a corporate site. I have been known to put knock-knock jokes in the meta description, or maybe I once used ieat7331 as a css class name, though it's been a while. Would anyone like to share/confess what they've seen/done, theoretically, if, say, you (or a "friend") had easter-egged somewhere at some time?

On the other hand, professional sites should look professional, inside and out - right? Does it bother you to see nerd humor in a html container on a big, corporate site?

Life is too short to not have fun.
Our credit card providers require we place a long winded terms of service notices on the sites and I have been known to place a $5.00 dollar reward or offer for a free item to the first person who contacts us. So far no takers.
As long as it's fun and not mean or hurtful or destructive, what harm can come of it?

I've embedded unique paragraphs of text in the ALT= attributes for some images. People using Internet Explorer or text-based browsers (such as Lynx or Lynx simulators) would be able to read the text but Chrome and Firefox users would not (kind of an anti-SEO joke, I guess).

Years ago I tested embedding text in comments on pages for Altavista, and that worked briefly until Altavista stopped indexing commented text (I only learned about the technique after many people in the SEO community complained openly about it). So I wrote this huge long diatribe about how people should not be looking under the hood of my Website and left it in the comment for about a year, maybe two.